Fix trace of TLSv1.3 Certificate Request message

A TLSv1.3 Certificate Request message was issuing a "Message length parse
error" using the -trace option to s_server/s_client.

Reviewed-by: Rich Salz <rsalz@openssl.org>
Reviewed-by: Ben Kaduk <kaduk@mit.edu>
(Merged from https://github.com/openssl/openssl/pull/5008)